After several years of operation, cracks and leaks often develop in the silica brick walls and roofs of coke ovens. Cracks in the oven walls are most common near the pusher and discharge ends of the ovens. The cracks are harmful in that they permit the passage of smoke emissions from the ovens to the flues and then to the battery stack. Cracks can also accelerate wall wear and cause hot spots that can result in the eventual shut-down of the oven. Effective oven sealing is now a virtual necessity to comply with existing or anticipated environmental demands. For a patching and sealing material to be effective, it should bond to the hot silica brick surface to which it is applied. Once applied, the material must have thermal expansion characteristics that are compatable with the silica brick in order that spalling of the coating on heating or cooling does not result. A number of commercially available materials are presently used for coke oven patching and sealing, but with varying and often unacceptable degrees of effectiveness. This ineffectiveness of the commercially available materials is primarily caused by their inability to develop a coherent, strong ceramic bond with the surface to be patched, particularly at what may be termed the moderate temperatures (less than 2400.degree. F.) that exist in coke ovens. U.S. Pat. No. 3,814,613, the disclosure of which is incorporated herein by reference disclosed a patching material which appeared to offer significantly improved bonding characteristics over the previously employed, commercially available patching materials. Thus, in laboratory tests employed to evaluate the bonding characteristics of such patching materials, the bonds formed by the '613 patented compositions appeared to show appreciable bonding under all test conditions. It has subsequently been found, however, that while the '613 patented composition was, in fact, superior in bonding to many commercially available materials; that its seemingly acceptable bonding (determined by laboratory test procedures) was not always borne-out in actual practice. As a result, new test procedures were developed. These new procedures were employed to evaluate a variety of patching mixtures and led to the finding that superior bonding under conditions similar to those encountered in coke ovens, could be achieved by the addition of a low melting phase, e.g. window glass, to the basic components (i.e. silicious aggregate and chemical binder) of the 3,814,613 patent.